1.（4x^2-25y^2）/(2x-5y) =(2x+5y)(2x-5y)/(2x-5y) =2x+5y 2.(2x^2-2x+1\2)/(x-1\2) =2(x^2-x+1/4)/(x-1/2) =2(x-1/2)^2/(x-1/2) =2(x-1/2) =2x-1 3.2x^2-3x=0 x(2x-3)=0 x=0或x=3/2 4.(3y+5)^2=4y^2 9y^2+30y+25=4y^2 5y^2+30y+25=0 y^2+6y+5=0 (y+1)(y+5)=0 y=-1或y=-5